1. Technical Field
Various embodiments of the present invention relates to an oscillator, an electronic apparatus, and a vehicle.
2. Related Art
A crystal oscillator, which is used for a reference frequency signal source for communication equipment, a measurement instrument, or the like, is required to have the output frequency stable with high accuracy with respect to a change in temperature. In general, there is known an oven controlled crystal oscillator (OCXO) as a crystal oscillator, with which extremely high frequency stability can be obtained, among crystal oscillators. Further, in recent years, an improvement in characteristic of the temperature compensated crystal oscillator (TCXO) is remarkable, and the TCXO having frequency accuracy and frequency stability close on those of the OCXO is under development.
Such an oscillator high in accuracy is used for, for example, a base station of cellular phones, and is required to be able to control the frequency with digital control in some cases. For example, in Japanese patent application JP-A-2011-101212, there is disclosed a piezoelectric oscillator, which has a D/A (Digital to Analog) converter, a resonator, and an oscillation loop, and the frequency output from which can be changed by changing the input signal to the D/A converter.
Further, in the case of the oven controlled crystal oscillator (OCXO) used in the base station or the like, there is required to output information such as an oven alarm signal, which represents the fact that the temperature has been stabilized and the oscillator has become available, in addition to the oscillation signal in some cases. For example, in JP-A-2014-192578, there is disclosed an oscillation device including an oscillator attached with an oven, which informs the outside of the fact that the oscillation frequency of the oscillation device has been stabilized after powered on.
However, in the case in which the D/A converter and the oscillation circuit are integrated into the same IC as in the case of the oscillator described in JP-A-2011-101212 in order to miniaturize the oscillator, there is a possibility that the noise caused by a communication signal as a digital signal gets mixed in the oscillation circuit through a roundabout way to deteriorate the noise characteristic of the oscillation signal.